Postretirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5	$ 2	$ 3
Interest cost	2,635	2,820	2,080
Expected return on plan assets	(3,311)	(3,441)	(3,789)
Amortization of prior service credits	(81)	(81)	(81)
Recognized net actuarial loss/(gain)	281	173	913
Settlement/curtailment gain			(4)
Net periodic benefit (income)/cost	(471)	(527)	(878)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	51	49	72
Interest cost	124	148	98
Expected return on plan assets	(10)	(9)	(10)
Amortization of prior service credits	(11)	(22)	(35)
Recognized net actuarial loss/(gain)	(176)	(175)	(111)
Settlement/curtailment gain
Net periodic benefit (income)/cost	(22)	(9)	14
Operating Income (Loss) | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	5	2	3
Operating Income (Loss) | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	47	62	79
Other Income | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	(476)	(529)	(881)
Other Income | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	(73)	(58)	(58)
Operating Income (Loss) Before Taxes | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	(471)	(527)	(878)
Operating Income (Loss) Before Taxes | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	$ (26)	$ 4	$ 21